“Taking full account of all the evidence and analysis available to me,” Judge Owen said in the report, “I find that the F.S.B. operation to kill Mr. Litvinenko was probably approved by Mr. Patrushev and also by President Putin.”

Treatment is limited to supportive care against the effects of the radiation, although chelation agents may be able to help eliminate polonium if a case of poisoning is identified early enough.

Chelation therapy is also likely to be beneficial, with research in animals suggesting reduced retention in the body and improvements in survival, although increased activity in some radiosensitive organs has also been reported with some chelating agents. Dimercaprol (British Anti-Lewisite) (with penicillamine as an alternative) is currently recommended for (210)Po poisoning, but animal models also indicate efficacy for 2,3,-dimercapto-1-propanesulfonic acid, meso-dimercaptosuccinic acid, or N,N -dihydroxyethylethelene-diamine-N,N -bis-dithiocarbamate.